To evaluate left ventricular diastolic function during dipyridamole-provoked myocardial ischemia, transmitral flow was studied in 73 patients with coronary artery disease and 8 normal subjects using pulsed Doppler echocardiography. Coronary vasodilating agents like dipyridamole can provoke myocardial ischemia in patients with coronary artery disease. The peak flow velocity of left ventricular rapid filling (R), that of atrial contraction (A) and the ratio of A to R (A/R) in each cardiac cycle were measured. The rapid filling phase was divided into two subphases at the point of R. The integral of the two subphases and atrial contraction were computed and designated IR1, IR2 and IA. The time intervals of the two subphases of rapid filling were designated TR1 and TR2. Of the 73 patients with coronary artery disease, 41 patients developed ischemia (positive responder = PR) and 32 patients did not (negative responder = NR) after dipyridamole infusion. In PR, A/R increased (p less than 0.05), IR2 decreased (p less than 0.01) and TR2 shortened (p less than 0.01) significantly. In NR and normal subjects, these indices remained unchanged. We observed mitral regurgitation (MR) in 13 PR patients during acute myocardial ischemia. A/R increased in patients without MR but A/R remained unchanged in patients with MR. These results suggest that in acute myocardial ischemia, changes in Doppler indices (A/R, IR2 and TR2) reflect a left ventricular diastolic abnormality, and that the masking of the diastolic abnormality was ascribed to the presence of MR.